Help! Stumped on maths question!

[Hollyhead]

DC has been working on this for 15 mins, we’ve tried trial and error but we’re both running out of steam!

Thanks everyone, those are the methods I tried but two crucial failures 1 - significant lack of patience - I probably needed to just be a bit more methodical for a few mins and 2. I hadn’t really thought about the logic of focusing on the largest pieces first. But thanks to all you I managed to help DC work it out without much support in the end 😁